A communication apparatus located within a general communication network equipped with a Layer 2 redundancy employs a STP (Spanning Tree Protocol) to form a blocking port in order to avoid loops in packet transfer. However, in the communication apparatus employed with the STP, since a path connected to the blocking port becomes unavailable while the loops may be avoided, an available bandwidth of the communication apparatus is unable to be effectively utilized.
Accordingly, TRILL (Transparent Interconnection of Lots of Links) which is a Layer 2 redundancy protocol is defined in RFC 6325 as a standard. TRILL is a technology which makes paths in a communication network, for example, Ethernet (registered trademark) redundant. Furthermore, since TRILL has architecture capable of avoiding loops in data transfer without forming the blocking port, more effective utilization of the available bandwidth may be achieved in TRILL than in STP.
TRILL may adapt an IS-IS (Intermediate System to Intermediate System) which is a Layer 3 routing protocol to Layer 2 to rapidly switch from an active path to a redundant path such as, for example, in the case where a fault occurs on the active path. The communication apparatus equipped with an L2 switch function which corresponds to TRILL has a function of determining the shortest path among physical paths within a TRILL network constituted with a plurality of communication apparatuses using a SPF (Shortest Path First) method.
Furthermore, since respective communication apparatuses of the TRILL network perceive the costs of respective physical paths within the TRILL network, the communication apparatus is also equipped with a function of autonomously switching from an active physical path to a least cost redundant path among a plurality of redundant paths that are able to allocate in a case where the active physical path within the TRILL network becomes unavailable due to, for example, a fault.
Further, a DCB (Data Center Bridging) of Ethernet extensions is known which intends to be used mainly in data centers and implements, for example, a lossless packet. In the meantime, the DCB is stipulated by IEEE (Institute of Electrical and Electronics Engineers).
Further, the DCB includes an ETS (Enhanced Transmission Selection) function. The ETS function is a protocol capable of classifying traffic into TCs (Traffic Classes) prioritized with a defined priority and designating an allocation ratio of the minimum guaranteed bandwidth for each TC to a physical bandwidth of a physical path (see, e.g., IEEE 802.1Qaz). Further, the TC corresponds to a category of traffics grouped based on similarity of traffic. The TC is allocated to a value of a PCP (Priority Code Point) field within a frame of traffic. The PCP field corresponds to a 3-bit field which designates a priority level defined in IEEE802.1p and indicates the priority level of the frame by 0 to 7 to assign the priority level to various traffics such as, for example, voice, moving picture or data. Accordingly, a higher priority TC is allocated to a packet of traffic such as, for example, storage I/O, for which the lossless packet is required such that the packet of traffic is preferentially allocated to the physical path, thereby achieving the lossless packet.
That is, the ETS function may be referred to as architecture that guarantees an allocatable minimum bandwidth for each TC among bandwidths of traffic to be allocated to the physical path and at least the minimum bandwidth is allowed to be allocated to a lower priority traffic to implement a bandwidth guaranty per TC unit.
Next, descriptions will be made on an example of setting of the ETS in detail. The traffic to be allocated to the physical path are classified into, for example, TC1, TC2, and TC3, and a predicted traffic amount of TC1 is set to 100 Mbytes/sec, a predicted traffic amount of TC2 is set to 200 Mbytes/sec, and a predicted traffic amount of TC3 is set to 100 Mbytes/sec. Further, the physical path is 1 GB line which provides 1 Gbytes/sec as the maximum traffic amount. ETS allocates 25% of a bandwidth allocation ratio for TC1 with respect to the physical bandwidth of the physical path, 50% for TC2, and 25% for TC3 according to the predicted traffic amount of each TC of the traffic to be allocated to the physical path. As a result, a traffic amount of a bandwidth for TC1 is guaranteed up to 250 Mbytes/sec, a traffic amount of a bandwidth for TC2 is guaranteed up to 500 Mbytes/sec, and a traffic amount of a bandwidth for TC3 is guaranteed up to 250 Mbytes/sec. In the meantime, the setting contents of the ETS, that is, the bandwidth allocation ratios for respective TCs are not changed as long as a user does not set and change the setting contents.
Further, in recent years, it is also being considered that the DCB and TRILL are used together to construct a robust communication network to be utilized in FCoE (Fibre Channel over Ethernet (registered trademark)) for consolidating such as, for example, a storage I/O for which the lossless packet is required.
A related technique is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2002-44147.